1. Field of Invention
The present invention generally relates to a disk drive apparatus and, more particularly, to a method for monitoring the flying height of a read/write transducer head relative to a disk surface.
2. Description of Related Art
Disk drives which are used, for example, in work stations, personal computers and portable computers, are required to provide a large amount of data storage within a minimum physical area. Generally, magnetic media type disk drives operate by positioning a read/write transducer head over tracks on a rotating magnetic storage disk. The positioning of the read/write head is accomplished by employing an actuator arm coupled to control electronics. The control electronics control the positioning of the actuator and the reading and writing functions of the transducer head.
Increasing storage capacity demands are being placed on disk drives. Computer systems are requiring disk drives to have higher storage capacity, while occupying a minimal amount of space within the computer system. In order to accommodate these demands, disk drives are being produced with reduced physical size and increased capacity.
One measure of determining the storage capacity of a disk drive is the flying height of the drive's transducer head above the drive's rotating storage disk. The flying height is the distance between the surface of the disk and the read/write head. In operation, a drive's disk achieves a certain angular velocity after start up of the drive, so that a cushion of air is generated above the disk's surface. This cushion of air forces the read/write head up off the surface of the disk to achieve a flying height. Having very small flying heights increases a drive's storage capacity, because flying the read/write head very close to the disk surface allows for high data bit density (i.e., the number of data bits per inch on a data track).
The largest data bit density can be obtained when the read/write transducer head contacts the disk surface. However, repeated contact between the read/write head and the disk surface results in damage to the head and disk. Thus, there has been an industry-wide trend to decrease the flying height in a disk drive without causing the read/write head to actually contact the disk surface.
However, as a read/write head flies over a rotating disk, the flying height does not remain constant, but rather tends to fluctuate slightly above and below a normal flying height. When flying heights are small, a variation in the flying height may cause the read/write head to randomly contact the disk surface. This situation is referred to as intermittent contact. Such repeated contact between the read/write head and disk surface can damage the head and disk. This damage can cause drive failures in an extremely short period of time. Such failures can result in the drive's user losing all of the data stored in the drive.
Accordingly, it is desirable to provide for determining whether the flying height of a read/write transducer head in a disk drive is so small that repeated intermittent contact is likely. When manufacturing disk drives, the ability to make such a determination provides for the testing of manufactured drives to ensure that the flying height is sufficiently large. During a disk drive's operation in the field, such a determination could be made to ensure that the drive is still operating with an acceptably large flying height. If the flying height of a user's drive is determined to be too small, the user can then be notified that the drive should be either serviced or replaced.